u/1971CB350

I posted earlier about a meter which suddenly had a large error. Here’s what it looks like inside. The adjusting forks had somehow moved beyond the adjusting screw, preventing the pointer from reading zero again. With the cover off, I gently nudged the adjustment fork to zero out the pointer. This type of ammeter was used in many configurations to represent many different metrics; in this case it is a ship’s propeller shaft tachometer.

This Weston/Metermod Model 273 ammeter is in use as a tachometer. It suddenly has an error of +30RPM. It responds to actual shaft speed appropriately. The adjustment screw on the front has no effect. Its twin in another space, on the same circuit, reads correctly. Is there another way of testing or adjusting this meter? Thanks for any advice.